Recently some documentation (finally) came available about how you can store huge files external to your SharePoint SQL database while using the rich feature set of SharePoint as an enhanced information store. To actually get this working you will need to implement a COM interface (ISPExternalBinaryProvider), which will keep your external storage and the SQL Content database(which will contain a pointer to the data as well as metadata about the object) in sync.
Available information:
Unfortunately the API is almost useless in the current version. I blogged about that:
ReplyDeletehttp://www.hezser.de/blog/Lists/Beitraege/ViewPost.aspx?ID=75
"With the current version only the SPFarm is supported. Meaning ALL content will be stored externally"